The invention relates to a procedure for controlling actuators within an on-board power system, which provides different operating voltages or temporal on-board power voltage changes.
The invention furthermore relates to a corresponding device for implementing the procedure according to the invention.
The controlling of the any actuator, for example a magnetic coil of a valve, or the operation of sensors in a motor vehicle depends on the control voltage and therefore on the on-board voltage of the operating system and on the capacity of the hardware of the actuator or the sensor.
The operating voltage or the on-board power voltage can vary between 6 V and 32 V, and higher. Current motor vehicles and motorbikes have a usual on-board power supply with an operating voltage of 12 V. trucks on the other hand have an on-board power supply with a 24 V operating voltage. For each of these different on-board power supplies an individual driver to be developed for the corresponding case of application and the corresponding hardware, in order to maintain an optimal functionality of the actuators or the sensors at complex control applications.
An example of a system with a complex controlling application for an actuator is a reducing agent metering system for an exhaust gas purification system of a diesel combustion engine, which is commercially available under the name DENOXTRONIC of the applicant. With this system, which is a central component of a SCR-system (selective catalytic reduction) and which has been successfully used in Europe since 2004 in heavy utility vehicles, the emissions of diesel engines can be significantly reduced. In order to reduce the NOx-emission (DeNox) of diesel engines, with temporally mainly lean, i.e. oxygen-rich exhaust gas, a defined amount of a selectively working reducing agent is added to the exhaust gas in this procedure. This can for example be in the form of ammoniac, which is directly metered in the form of gas, or is also won from a precursor in the form of urea or of a urea-water solution. Such urea-water solution SCR-systems have been first used in the utility vehicle segment. DE 10139142 A1 describes an exhaust gas purification system of a combustion engine, at which a SCR-catalytic converter is used for reducing the NOx-emissions, which reduces nitrous gases that are contained in the exhaust gas with the reducing agent ammoniac to nitrogen. The ammoniac is won in a hydrolysis catalytic converter arranged upstream in front of the SCR catalytic converter from the urea-water solution, consistently called AdBlue® in the industry. The hydrolysis catalytic converter converts the urea contained in the urea-water solution to ammoniac and carbon dioxide. In a second step the ammoniac reduces the nitrous gases to nitrogen, whereby water is produced as side product. The exact process has been sufficiently described in the technical literature (compare Weissweller in cit (72), page 441-449, 2000). The urea-water solution is provided in a reducing agent tank. In this concrete case the actuator is the magnetic coil of the injection valve, which is built into the exhaust gas system of the diesel combustion engine and with which the urea-water solution can be injected in doses into the exhaust gas system.
Up to now profound hardware adjustments and software changes are required in order to adjust to the corresponding field of application with different on-board power supplies. Injection valves, which are for example construed for an on-board power supply with 12 V, cannot be operated without further ado at 24 V on-board power supply. So far another valve had to be built in at a control unit hardware defined for it, which is especially construed for 24 V or 12 V, and, within the range of the application software, another injection driver or an additional voltage divider.
With regard to a higher flexibility at the application and a reduction of the adjustment developing costs regarding the soft- and hardware that have been required up to now, it is the task of the invention to provide a procedure, with which a controlling of actuators is enabled that is independent of the on-board voltage.
It is furthermore the task of the invention to provide a device for implementing the procedure.